How do I detect that a SWT dialog has been opened and is visible?

Question

I have an SWT WizardDialog with a number of pages. When this dialog first opens I have to do a check for some conditions and if those conditions are met I need to show a popup over the freshly opened dialog.

So I have this code to listen for SWT.Show event. The event listener responds to SWT.Show to conduct its tests and show a message box:

  final WizardDialog dialog = new WizardDialog(shell, wizard);
  dialog.setTitle("New Wizard");
  dialog.create();
  dialog.getShell().addListener(SWT.Show, new Listener()
  {
     private boolean firstShowing = true;

     @Override
     public void handleEvent(Event event)
     {
        if (firstShowing && someConditionExists())
        {
          MessageBox messageBox = new MessageBox(dialog.getShell(), SWT.OK
                 | SWT.ICON_WARNING);
          messageBox.setMessage("Test");
          messageBox.open();
          firstShowing = false;
        }
     }
  });
  dialog.open();

Except it's called too soon! The dialog is not visible when the handler is called. My message box appears before the dialog is visible and the dialog only appears when I dismiss the message box.

So clearly the SWT.Show is unreliable, at least on Windows where I'm running it. I've also tried putting this code into a ShellListener on the activation but that happens even before the SWT.Show example above.

So how do I reliably show a message box when the dialog is made visible?

Plan B is a dirty timer based hack where a timer is set to fire 200 ms into the future and hope that it triggers when the dialog is visible but obviously this could introduce it's own issues.

Answer 1

I'm using in similar situation (need that appStarted() is called after application window is visible) something like below.

public class App extends ApplicationWindow {

    @Override
    protected Control createContents(Composite parent) {
        // ...

        getShell().addShellListener(new ShellAdapter() {

            @Override
            public void shellActivated(ShellEvent shellevent) {
                if (!started) {
                    Shell s = (Shell) shellevent.getSource();
                    s.setVisible(true);
                    appStarted();
                    started = true;
                }
            }
        });
    }
}

Maybe You can use the same like below:

final WizardDialog dialog = new WizardDialog(shell, wizard);
dialog.setTitle("New Wizard");
dialog.create();
dialog.getShell().addShellListener(new ShellAdapter() {

    @Override
    public void shellActivated(ShellEvent shellevent) {

        if (firstShowing && someConditionExists()) {
            Shell s = (Shell) shellevent.getSource();
            s.setVisible(true);

            MessageBox messageBox = new MessageBox(dialog.getShell(), SWT.OK | SWT.ICON_WARNING);
            messageBox.setMessage("Test");
            messageBox.open();
            firstShowing = false;
        }

    }
});
dialog.open();

Answer 2

Instead of hooking the SWT.Show event, you may get more luck with hooking a PaintListener on to your dialog's Composite. (You'll probably want to unhook it during the first execution.)